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Proceedings Paper

High temperature thermographic measurements of laser heated silica
Author(s): Selim Elhadj; Steven T. Yang; Manyalibo J. Matthews; Diane J. Cooke; Jeffrey D. Bude; Michael Johnson; Michael Feit; Vaughn Draggoo; Scott E. Bisson
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Paper Abstract

In situ spatial and temporal surface temperature profiles of CO2 laser-heated silica were obtained using a long wave infrared (LWIR) HgCdTe camera. Solutions to the linear diffusion equation with volumetric and surface heating are shown to describe the temperature evolution for a range of beam powers, over which the peak surface temperature scales linearly with power. These solutions were used with on-axis steady state and transient experimental temperatures to extract thermal diffusivity and conductivity for a variety of materials, including silica, spinel, sapphire, and lithium fluoride. Experimentally-derived thermal properties agreed well with reported values and, for silica, thermal conductivity and diffusivity are shown to be approximately independent of temperature between 300 and 2800K. While for silica our analysis based on a temperature independent thermal conductivity is shown to be accurate, for other materials studied this treatment yields effective thermal properties that represent reasonable approximations for laser heating. Implementation of a single-wavelength radiation measurement in the semi-transparent regime is generally discussed, and estimates of the apparent temperature deviation from the actual outer surface temperature are also presented. The experimental approach and the simple analysis presented yield surface temperature measurements that can be used to validate more complex physical models, help discriminate dominant heat transport mechanisms, and to predict temperature distribution and evolution during laser-based material processing.

Paper Details

Date Published: 31 December 2009
PDF: 13 pages
Proc. SPIE 7504, Laser-Induced Damage in Optical Materials: 2009, 750419 (31 December 2009); doi: 10.1117/12.836985
Show Author Affiliations
Selim Elhadj, Lawrence Livermore National Lab. (United States)
Steven T. Yang, Lawrence Livermore National Lab. (United States)
Manyalibo J. Matthews, Lawrence Livermore National Lab. (United States)
Diane J. Cooke, Lawrence Livermore National Lab. (United States)
Jeffrey D. Bude, Lawrence Livermore National Lab. (United States)
Michael Johnson, Lawrence Livermore National Lab. (United States)
Michael Feit, Lawrence Livermore National Lab. (United States)
Vaughn Draggoo, Lawrence Livermore National Lab. (United States)
Scott E. Bisson, Sandia National Labs. (United States)

Published in SPIE Proceedings Vol. 7504:
Laser-Induced Damage in Optical Materials: 2009
Gregory J. Exarhos; Vitaly E. Gruzdev; Detlev Ristau; M. J. Soileau; Christopher J. Stolz, Editor(s)

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